Heating apparatus



Feb. 16, 1937. R PAYSON HEATING APPARATUS Filed April 6, 1935 INVENTOR.

A TTORNEY Patented Feb. 16, 1937 UlTED STATES ATENT OFFICE 3 Claims.

My invention relates to heating devices. In most heating plants, especially those for heating houses and apartments, there is usually a boiler which is heated either by a coal or oil fire and either the water from the boiler or steam generated from the water is circulated through radiators for the purpose of heating the air in the various parts of the building. In most installations the apparatus operates at a low rate of efiiciency because only a small percentage of the generated heat is utilized. A large percentage of the heat generated by the combustion of the fuel passes oif as waste through the smoke stack, and this is evidenced by the fact that the tem- 5 perature in the stack'is usually around 700 to 1100 degrees, showing that only a relatively small portion of the total heat generated is actually utilized in raising the temperature of the water in the boiler.

The object of my invention is to utilize for economic purposes a very substantial portion of the heat which usually passes out with the products of combustion into the stack to be discharged into the open air. I have provided an apparatus wherein water is heated by the heat carried by the products of combustion after leaving the fire box of the steam plant, so that the heat which ordinarily would pass out of the stack is utilized to a large extent in the heating of a body of water or other fluid.

The efliciency of the present device may be appreciated when it is understood that the temperature in the stack at a position beyond my present device will ordinarily be reduced to about 300, whereas in equipment which is not supplied with my apparatus, the stack temperature would ordinarily be about 700 to 1100. From this it is obvious that I am enabled to utilize a large percentage of What would otherwise be wasted heat,

While the present apparatus may be employed in connection with any type of boiler, its principal adaptation will be in connection with heating plants used in private homes and in apartment buildings, because such apparatus are usually 5 less efiicient than very large heating plants and there is, therefore, an opportunity for a larger percentage of conservation of heat.

The water in the present apparatus may be heated and circulated as hot water through suit- 50 able radiators for heating portions of a building, or the water may be heated to a point where steam is generated in the upper portion of the liquid compartment and this steam as such may be circulated through suitable radiators for heat- 5 ing portions of a building. On the other hand,

the present apparatus may be used to provide a hot water supply independent of the usual heating apparatus, in order to supply hot water for household or other purposes.

If desired, the water heated in the present apparatus may be fed into the boiler of the regular heating plant to augment its supply of steam or hot water to the distributing portion of the system, or steam generated in the present apparatus may be fed into the steam chamber of the boiler 9 or" the regular heating apparatus. Or, the heated water or steam may be taken directly from the present apparatus and fed into radiators which are independent of the radiators supplied by the regular boiler of the system. 5

Thus, the present apparatus is adapted to supply hot water or steam which 'may be utilized in various ways, the main object being to utilize a large portion of the heat which ordinarily passes out of the fire box of an ordinary steam or water boiler.

The present apparatus is simple, inexpensive, and it is very compact in size considering the results accomplished with it. The apparatus may be connected with the ordinary flue outlet of the regular heating plant and at any convenient location, preferably Within the cellar or basement where the regular heating plant is located, in order to be as close as possible to the fire box of the regular heating equipment. The present ap- 3O paratus is preferably constructed independently of the regular heating system to be connected in the flue in order to adapt the device to various heating plants now in general use, and also to avoid complicating the construction of the regular heating equipment.

, The present device is adapted to operate to extract and utilize a large portion of what otherwise would be wasted heat and without interfering with or obstructing the draft necessary for the operation of the fire of the regular heating system.

In the apparatus containing the present invention the heated products of combustion from the furnace of the heating plant are passed through ducts in the body of liquid which is to be heated, and then the products of combustion are returned in a reverse flow around the exterior of the body of liquid.

In this manner a device of practical length will suffice to transfer a large portion of the heat from the heated products of combustion to the body of liquid which is to be heated. As far as I am aware, this is the first instance where the products of combustion have been caused to flow reversely in relation to the body of water to be heated. This reverse flow of the products of combustion takes place in the present apparatus in such manner that it does not obstruct the draft in the fire box and therefore it does not materially affect the proper combustion of the fuel.

Other features and advantages will be pointed out in the following description of several forms of my invention.

In the drawing forming part of this application,

Figure l is a longitudinal, sectional View through a heating apparatus embodying my invention in one form, and it is taken on the line |I of Figure 2,

Figure 2 is a sectional view thereof taken on the line 22 of Figure 1,

Figure 3 is a sectional view taken on the line 33 of Figure 2,

Figure 4 is a view similar to Figure 1 but showing my invention embodied in a modified form, the View being taken on the line 4-4 of Figure 5,

Figure 5 is a sectional View taken on the line 5-5 of Figure 4,

Figure 6 is a view similar to Figures 1 and 4 but showing a modified form of the invention, and it is taken on the line 6-6 of Figure '7, and

Figure '7 is a sectional view taken on the line of Figure 6.

I will first describe the form of the invention shown in Figures 1 to 3 inclusive.

I have shown an outer shell of cylindrical form consisting of a cylindrical wall I which is closed at one end by means of a head 2; having a fiange 2 fitting the end of the cylinder I which head may be removed for cleaning the tubes. At the left hand end of this enclosure in Figure l. I have provided a removable head t which is also fitted on the end of the cylindrical body.

Within the enclosure just described there is preferably mounted a cylindrical member 6 which is of smaller diameter than the outer cylinder 1, and it is shown as disposed concentric with the latter to provide an annular space 1 between the two cylindrical members. Preferably there are radial plates 8 extending longitudinally in the annular space I, there being four such plates shown in the drawing, and these plates extend from the right hand end of the cylindrical member 6 to a point which is some distance from the extreme left hand end of the cylindrical member I.

The left hand end of the cylindrical member 6 as viewed in Figure l is fitted in a central aperture in the head 4, thus closing the annular space 1 between the inner and outer cylindrical members at one end of the apparatus. The right hand end of the cylindrical member 6 terminates some distance from the closed head 2. The cylindrical members i and 6 may be supported in any desired manner either from a wall or from a floor or beam. I have shown in the drawing the cylindrical members supported upon a structure 9 in the following manner.

In the annular space i between the cylindrical members I have provided short posts it the bottom ends of which rest on the inner surface of the outer cylindrical member I and the upper ends are provided with curved caps or heads H in which the outer surface of the cylindrical member 55 rests so that by means of these posts the inner cylindrical member is supported upon the outer cylindrical member. The longitudinally extending plates 8 which are disposed radially in the annular space 1 may also be united with the cylindrical members by brazing, welding or otherwise, and they tend to retain the cylindrical members in concentric relation although they perform other functions as will be set forth hereinafter.

Below the outer cylindrical member I I have provided posts I2 having feet It to rest on the structure 9 and the upper ends of these posts are shown as provided with heads or caps Id of arcuate shape which seat against the under surface of the outer cylindrical member I, to which they may be welded if desired, so that the whole structure is supported upon the posts l2 and the inner structure or cylinder 6 is supported by the posts Ill as well as by the posts [2 which are preferably in line therewith. I have shown in the drawing two supporting devices of the character just described, one near each end of the apparatus, but it will be understood that there may be additional supporting devices disposed at any desired positions along the apparatus; and it will be also understood that the supporting devices may be modified to suit various conditions such as where the apparatus is to be supported from cei ing or wall beams.

At the left hand end of the apparatus in Figure l I have shown the line pipe l5 having an enlarged or fiared end IS with a cylindrical portion ll fitting closely into one end of the cylindrical member 6.

This pipe is preferably the pipe which is connected with the regular heating apparatus or furnace (not shown) and by which the products of combustion which pass on" from the regular heating furnace will be fed into the left hand end of the cylindrical member 6.

Adjacent the left hand end of the apparatus in Figure 1, I have provided a head l8 fitting the interior of the cylindrical member 6 and at the opposite end of the cylindrical member 6 I have provided another plate or head l9 which also fits the perimeter of this cylindrical member to form fluid-tight connection therewith. There are various tubes which are open at each end and are mounted between the heads to align with corresponding apertures in the heads. While various sizes and forms of tubes may be used, I have shown in Figures 1 to 3 a relatively large tube 28 arranged concentric of the cylinder 5 and in line with the axis thereof. This tube is mounted at opposite ends in the two heads l8, is either by welding, brazing or otherwise, and the heads each have apertures conforming with the size of this tube, so that some of the products of combustion entering from the pipe l5 may pass through the left hand head 18 and through the tube 28 to emerge at the right hand end of the latter tube in the space 2! inside the head 2 of the outer shell. The products of combustion thus discharged into the space 2! will be disposed of in the manner hereinafter described.

I have shown other tubes 22 of relatively smaller diameter than the central tube 26 and these are all mounted at opposite ends in the two heads l8, l9 and in line with corresponding openings in the heads. These tubes are shown in Figures 1 to 3 disposed in circular order in the annular space 23 between the larger central tubeas and the cylindrical member 6.

These tubes perform the same function as the larger tube as; that is to say, some of the products of combustion introduced through the pipe l5 pass through these smaller tubes and emerge in the space 2! similar to the action of the portion which travels through the central tube 20.

The water or other liquid to be heated is circulated in the space 23 between the several tubes just described and the cylindrical member ii. I have shown the feed pipe 24 which passes through the cylinder wall l of the outer casing, the connection being such as to prevent the escape of fluid, and one end of this pipe is connected with the inner cylindrical member 5 the latter having an opening registering with the end of the pipe 24 so that water or other liquid to be heated is introduced by this pipe into the space 23 which includes the space between all of the tubes 20, 22 and the cylinder 6. I have shown the level of this water at 25 which is approximately the level at which the apparatus will operate when steam is to be delivered from the water heated within the apparatus. It will be understood that if the device is used to heat water without necessarily forming steam, that is to say, where the device is used for supplying hot water only, then the space 23 will be entirely filled with water.

The water or steam, as the case may be, is withdrawn from the space 23 through a pipe 26 which extends through the outer shell I and is connected with the inner shell 6, the latter being supplied with an aperture registering with the end of the pipe. Preferably, this pipe is relatively larger in diameter than the supply pipe 2 3 and it is preferably arranged toward the left hand end of the apparatus in order that the water supplied to the space 23 will travel not only from the bottom to the top of the space but also travel lengthwise of the apparatus.

Adjacent the left hand end of the apparatus in Figure l I have shown the pipe or stack 2! connected with the outer shell and with its interior communicating with the annular space 7 between the inner and outer shells. This pipe is adapted to conduct away the products of combustion after they have passed through the present apparatus and have been utilized for the purposes herein described.

Operation The products of combustion that discharge from the fire box of the heating plant pass through the stack pipe l5 and are delivered into the left hand end of the apparatus shown in Figure 1; that is; into the space 29 at the left of the head It. These hot products of combustion will pass through not only the large central tube 26 but also all of the tubes 22 entering the open ends of these tubes adjacent the head l8. These products will pass through all of these tubes and will emerge from them in the space 2! between the head l 9 and the head 2 of the outer shell. While these products of combustion are passing through these several tubes they serve to heat the body of liquid contained in the space 23 the heat being conducted through the walls of the tubes to the liquid, thereby raising the temperature of the liquid within the space 23. After the products of combustion have been delivered into the space 2| they are prevented from discharging by the head 2 and they partake of a reverse flow or from right to left in Figure 1. These products of combustion will pass through the annular space 7 between the inner and outer cylinders.

The several radial plates 8 which divide this annular space into several segments will prevent the immediate rise of all of the products of combustion to the upper portion of the annular space I, or in other words, it will cause the products of combustion to travel in all of the segmental spaces 38.

These products will pass from right to left in Figure l in contact with the outer surface of the cylindrical shell 9 which contains the body of liquid which is to be heated and on this return flow the products of combustion deliver additional heat by conduction through the wall of the cylinder 6 to the body of liquid in the space 23, thereby further heating the water or other fluid.

The products of combustion will travel in this manner to the left hand ends of the several plates 8 and as these terminate approximately in line with right hand portion of the stack 21 all of the products which pass through the segmental chambers 33 will unite and will travel upwardly in the annular space 7 and pass out through the stack 2? to be discharged from the chimney or in any other manner which it is desired to dispose of them. By the time the products of combustion reach the stack 2'! they will have given up a large portion of their heat to the water in the space 23 and I have found that with an apparatus proportioned as substantially shown in the drawing, the temperature in the stack 21 may be as low as 300 indicating that a large portion of the heat carried by the products of combustion has been transferred to the body of liquid.

If it is desired to generate steam in the present apparatus, it will be understood that water will be supplied through the pipe 2 5 to maintain the level somewhat below the top of the cylindrical member ii, that is, in the space 23, to allow a free space in which steam may'be formed, in other words, a vaporizing space. In such case the water in the space 23, when heated, will form steam in the space 3! and this steam will pass out through the discharge pipe 26. This latter pipe may lead the steam to radiators in the building in which the apparatus is used or, if desired, it may beconnected with the boiler of the heating apparatus to augment the latter instead of the steam being directly used for radiation.

It is possible to utilize the steam in either of these two methods. It will be understood that if it is desired merely to supply hot water from the present apparatus, the water admitted through the pipe 24 will be unrestricted and it will entirely fill the space 23 as well as the pipe 26 so that the heated Water will pass out of the latter and flow to the place of consumption.

It is preferable, in order to avoid bafiiing the products of combustion, that the combined cross sectional areas of all of the tubes 20, 22 be equal to or else somewhat greater than the cross sectional area of the stack pipe i5. It is also desirable that the cross sectional area of the annular space 7 between the inner and outer shells be equal to or greater than the combined cross sectional areas of all of the tubes 2e, 22. It is preferable also that the exhaust stack 21 be as large or even larger than the cross sectional area of the pipe l5.

While the course of travel of the products of combustion through the present apparatus is not direct but is reversed in direction by reason of the passage through the tubes 20, 22 and backwardly through the annular space i, nevertheless there is but slight bafiiing of the products of combusition in their travel, especially if the proportions referred to above are observed; and therefore the passage of the products of combustion through the present apparatus does not materially interfere with the draft in the fire box of the heating plant with which the present apparatus is associated. Furthermore, the transfer of heat from the products of combustion to the body of water in the space 23 while those products are passing through the apparatus, has the effect of reducing the speed of the products of combustion due to their contraction, and this reduction in speed of the products of combustion more than offsets any slight bafliing action due to the reverse flow of the products of combustion.

In Figures 4 and 5 I have shown a modified form of the invention in which the same principles of operation are involved. In this view I have shown the outer shell the same as in the first construction, including the cylindrical wall 33, the head 3? and the head 32 at the left end of the apparatus. There is an inner cylindrical shell 33 which is also spaced concentrically with the outer shell 36 to provide an annular space M and preferably radial plates 35 are disposed in this annular space similar to the radial plates 8 in the first construction. They extend from the right hand end of the inner shell 33 to the left and terminate in a plane adjacent the right edge of the stack 38. I have shown an inlet pipe 39 and an outlet pipe 58 corresponding with the pipes 24, 26 in the first construction for admitting water to the interior of the cylindrical member 33 and for conducting away the steam or hot water.

, Within the cylindrical shell 33 and preferably concentric therewith there is a third cylindrical member ii and spaced from it to provide the annular space 62 which is the space actually containing the supply of water to be heated and which-is introduced by the pipe 39. This cylindrical member M is mounted at one end in the head 32 the latter having an opening correspond ing with it. The other end of the cylindrical member 33 is mounted in the right hand head 43 the latter having an opening corresponding with the diameter of the cylindrical member ii.

I have shown a series of small tubes id extending in a vertical row along the interior of the cylindrical member ll. The lower ends of these tubes are connected with the lower portions of the cylindrical member ll by liquid-tight joints which may be made by Welding, brazing or otherwise, there being an aperture in the lower portion of the cylindrical member ll in line with each of the tubes, so that the interior of these tubes is in open communication with the annular space Q2. The upper ends of the tubes, which are open, are connected with the upper portion of the cylindrical member iii by liquid-tight connections so that the upper ends of the tubes are in communication with the upper portion of the annular space 32. In this form of the invention the products of combustion are introduced from the stack pipe d5 which, it is understood, will be connected with the fire box of the regular heating equipment, and these products of combustion will pass through the cylindrical member M from left to right in Figure 4. While these products of combustion are thus travelling through the cylindrical member, some of the heat will be conducted through the wall of the member ll to heat the water in the annular space d2. Some of this heat will also be conducted through the walls of the several tubes it around which the products of combustion circulate, while passingthrough the cylindrical member All so that by the time the products of combustion reach the right hand end of the cylindrical member 4! a large part of the heat will have been transferred to the Water in the annular space 42. The tubes Mi may be omitted if desired.

When the products of combustion have passed through the cylindrical member 4| and through the opening in the head 43 these products will enter the space on the left side of the head 37 and will spread out and will be caused to flow in a reverse direction through the annular space 34, that is, through each of the segmental spaces formed between the radial plates 35. The products will thus travel from right to left in Figure 4 to the left hand ends of the radial plates 35 when the various portions of the products of combustion will merge and pass out through the delivery stack 33.

While these products of combustion are thus travelling in a reverse flow through the segmental spaces 3%, more heat is being conducted from these products of combustion to the water in the space 42 through the wall of the shell 33 thereby serving to further heat the water.

If it is intended to deliver steam from the annular space 3 then the water level will be maintained at a line which will allow a space at the top for the formation of the steam so that steam will flow out through the discharge pipe 43 to be disposed of as set forth connection with the first form of my invention. This form of my invention, while differing in structural characteristics from the first described form, nevertheless embodies the same principle of operation.

The products of combustion are not only caused to flow through the interior of the annular body of Water but are also reversed in direction of flow and thence travel in contact with the outer portion of the shell 33 wherein the water is contained. There is thus a long course of travel for the products of combustion in an apparatus of reasonable dimensions.

It will be understood that the outer shell of either of the above described apparatus may be covered with insulating material, if desired, to conserve the heat within the apparatus or, in other words, to prevent the exterior air from cooling the outer shell.

In Figures 6 and '7 I have shown a further modification of my invention. In this construction the outer shell @8 is shown as oval in cross section. One end of this shell is closed by a detachable head 49 while the opposite or left hand end is closed by a detachable head 50 which has an opening to receive the flared end 5| of a stack pipe 52 which conducts the products of combustion from the fire chamber of the heating apparatus into the present apparatus.

There is an inner shell 53 which I have shown as of oval shape and disposed concentric with the outer shell 48 to form an annular space 54 between the two shells. I prefer to provide radial plates 55 between the inner and outer shells but in this construction the radial plates are somewhat differently disposed than in the previous constructions as will be pointed out hereinafter. In the lower half of the compartment 5% within the shell 53 I have shown a relatively large centrally located tube 51 extending horizontally, with one end attached to the left hand head 53 the latter having an aperture corresponding With the diameter of this tube. The right hand end of this tube is connected with the right hand head 53 which also has an aperture corresponding with this tube. I have shown various other tubes 68 of different diameters disposed longitudinally and grouped around the larger tube 51 and these smaller tubes also have each one end mounted in the head 59 and their opposite ends mounted in the head 58, the heads having openings corresponding with the ends of the tubes.

In the upper portion of the compartment 58 I have shown a relatively large central tube 6! extending horizontally and having its opposite ends mounted in the heads 55, 59 which have apertures corresponding with the size of the tube. Grouped around this large tube I have shown various other tubes 62 in the space 56. These smaller tubes also have their mounted in the heads 58, 59 which latter have apertures to correspond with the several tubes. In this construction I have shown the water feed pipe 63 extending through the outer shell 48 and connected with the inner shell near the right hand end of the apparatus in Figure 6.

, The steam or hot water outlet pipe 64 is also shown as extending through the outer shell connected with the inner shell, this pipe being disposed adjacent the left hand end of the apparatus in Figure 6.

The stack 65 is shown connected with the outer shell 38 but in this instance it is disposed near the right hand of the apparatus in Figure 6 for a purpose which wfll be set forth.

Water fed through the pipe 63 will circulate through the chamber 55 in the shell 53 and will fill the space surrounding the various tubes except for steam space in the top cf the chamber. The hot products of combustion from the heating system will be admitted through the stack pipe 52 into the space at the left of the head 59 and below the plates 55 These particular plates extend the full distance between the left hand head 5!] and the right hand head 49.

Some of the products will pass through the opening into the annular space 54 between the lower half of the shell 53 and the outer shell 48. Part of the products will also pass through the tube 5'? and the smaller tubes 69 and will emerge in the space Ill between the head 58 and the head 49. The upper half of the shell 53 extends to and lies in contact with the head 49. The products of combustion, after passing through the tubes 51, S0 and the space 54, therefore, after entering the space 10, rise but they cannot pass directly out of the stack as they are prevented from doing so by the extended end at the upper half of the shell 53. These products, therefore, will pass from right to left through the tube 6| and the tubes 62 until they reach the left ends of these tubes and pass into the space ll between the head 59 and the head 50.

From there the products of combustion again reverse in their direction of movement and travel from left to right through the segmental portions of the annular space 54 between the shell 53 and the outer shell 48 which lie above the plates 55*. The upper plates 55 extend toward the right from the head 59 on the center shell and terminate in a vertical plane adjacent the left hand edge of the stack 65 so that when the products pass beyond the right hand ends of the plates 55 they will rise and pass off through the stack.

All of the tubes 51, 50, 6| and 62 are surrounded by the water in the chamber 56. Therefore, as the products of combustion pass through the tubes 51 and 65 and the space 54 heat is transferred to the interior and exterior of the body of liquid in the chamber 58. Then, as the products of combustion pass from right to left through the tubes GI and 62, more heat is conducted through these tubes to the water in the upper portion of the chamber 56. Then, as the products of combustion pass forwardly or from left to right in Figure 6, more heat is conducted through the wall of the shell 53 to the liquid in the upper portion of the chamber 56. In this device the products of combustion are passed at least three times along the apparatus, increasing the time in which heat is transferred from the products of combustion to the water. This apparatus is shown as disposed in a horizontal position although it can be operated also in a vertical or upright position. i

I do not wish to be limited to the size and proportions of the apparatus described herein but I will here set forth the proportions of apparatus which I have built and tested, together with the results obtained, in order to indicate the advantages derived from the invention. When the regular heating plant was operated without my device, at a time when the outdoor temperature was 45 and the interior of the house was 69 after operation for one hour and 14 minutes the house temperature was raised from 69 to 71.

The device built according to- Figures 1 to 3, in which the shell 5 was 45" long and 11 in diameter outside, is provided with seven tubes 22 of No. 14 gauge metal and with the tube 23, 4" in diameter and 14 gauge metal, the tubes and shells being made of steel. The outlet pipe 26 was connected with a radiator independently of the radiators heated by the regular boiler. In the instance cited the radiator was connected by a two-pipe system with the present apparatus.

Upon starting the apparatus with the products of combustion supplied from a household steam plant (oil burner heated) steam in the present apparatus was generated within 18 minutes to a pressure of 2 lbs. and fed into a radiator of 75 sq. ft. radiation, which it maintained hot. After this device had operated for one half hour the steam pressure reached ten pounds.

The apparatus was then operated in connection with my device as shown in Figures 4 and 5.

The operation started when the outdoor temperature was 35 and the house temperature was 66. After operating the regular heating system plus my apparatus for 45 minutes, the house temperature was raised 2 and after an operation of one hour and 14 minutes the house temperature was raised 4. It will therefore be apparent that with my apparatus combined with the regular heating boiler, the house temperature rose much faster than with the regular boiler without the present device.

In a device constructed as shown in Figures 4 and 5 the shell 33 was 11 in diameter outside and 45" long and the member 4! was 9" in diameter. When this device was operated with the regular steam boiler the steam generated in the apparatus shown in Figures 4 and 5 was led by a pipe into the steam chamber of the regular boiler and mixed with the steam generated therein.

After the regular heating system, together with my present apparatus, have been in operation and the room temperature has been brought to the desired degree, then the present apparatus and the regular boiler will serve to maintain the temperature with a lower consumption of fuel than where the regular boiler alone is used and the saving will be 16% or more.

By passing the products of combustion through the body of water and then backwardly around the body of water in the reverse direction, I am enabled with an apparatus of relatively small dimensions to utilize much of the heat which would ordinarily pass out of the stack and be wasted. While I have shown a number of tubes M in the construction shown in Figures 4 and 5 connected across the cylindrical member 4 I, it will be apparent that these tubes might be omitted and the entire body of water contained in the space 42.

Having described my invention, what I claim is:

, l. A device forutilizing heat in the products of combustion discharge-d from the fire box of a heating system, including a cylindrical outer shell having heads at opposite ends, a cylindrical inner shell mounted in said outer shell and spaced therefrom to provide a duct for the passage of the products of combustion, said inner shell being mounted at one end in one of the heads of said outer shell and terminating in spaced relation to the opposite head of said outer shell, said inner shell forming a liquid chamber, a tube of relatively large diameter centrally located and extending lengthwise through the body of liquid in said inner shell, other tubes of relatively smaller diameter arranged between said relatively large tube and the wall of said inner shell, means for conducting the products of combustion into one end of said tubes whereby said products will pass through said tubes, said products adapted to pass from the opposite ends of said tubes into the annular space between the inner and outer shells and to pass lengthwise along and in contact with said inner shell.

2. A device for utilizing heat in the products of combustion discharged from the fire box of a heating system, including an elongated, outer cylindrical shell having heads at opposite ends, an inner cylindrical shell disposed in said outer shell and spaced therefrom to provide a passage surrounding said inner shell, said inner shell forming a liquid compartment, tubes disposed in said inner shell and extending lengthwise through the body of fiuid therein and terminating in spaced relation to one head of said outer shell, means for conducting the products of combustion for delivering into the opposite ends of said tubes, whereby the products of combustion will pass through said tubes and thence pass in a reverse direction through the space between said inner and outer shells and in contact with said inner shell, a stack for conducting off the products of combustion adjacent the end of the device in which the products of combustion are introduced into said tubes, and radial plates disposed lengthwise in the space between said inner and outer shells and extending from adjacent the end of said inner shell in which the products discharge from said tubes, to a plane adjacent said discharge stack.

3. A device for utilizing heat in the products of combustion discharged from the fire box of a heating system, including an elongated, outer cylindrical shell having heads at opposite ends, an inner cylindrical shell disposed in said outer shell and spaced therefrom to provide a passage surrounding said inner shell, said inner shell forming a liquid-compartment, tubes disposed in said inner shell and extending lengthwise through the body of fluid therein and terminating in spaced relation to one head of said outer shell, means for conducting the products of combustion for delivering into the opposite ends of said tubes whereby the products of combustion may pass through said tubes and thence pass in a reverse direction through the space between said inner and outer shells and in contact with said inner sheil, and radial plates disposed lengthwise in the space between said inner and outer shells and extending from a point adjacent the end of said inner shell in which the products discharge from said tubes a substantial part of the length of said tube.

RUDOLPH PAYSON. 

